FIG. 23 is a sectional schematic view of a conventional electromagnetic relay (electromagnet relay) 500. Electromagnetic relay 500 includes electromagnet device 530 and contact device 520. Electromagnet device 530 includes coil 502, movable element 503 (plunger), permanent magnet 505, and overcurrent detection coil 513. Coil 502 attracts and drives movable element 503. Permanent magnet 505 is disposed facing movable element 503. Contact device 520 for attracting and holding movable element 503 includes fixed contact 510, movable contact 511, and contact spring 512.
When a voltage is applied to coil 502, movable element 503 is attracted by permanent magnet 505. Thereby, fixed contact 510 and movable contact 511 are brought into contact with each other, and contact device 520 is turned on. Then, even after excitation of coil 502 is released, movable element 503 is held by magnetic flux of permanent magnet 505, and contact device 520 is continued to be on.
When an abnormal current such as an overcurrent and a short-circuit current flows into contact device 520, movable element 503 is driven by overcurrent detection coil 513 in a reverse direction to permanent magnet 505, and contact device 520 is turned off. Thus, electromagnetic relay 500 forcibly restores movable element 503 by using magnetic flux generated when an abnormal current flows. That is to say, electromagnetic relay 500 can detect generation of an abnormal current and disconnect an electric circuit. As prior art literatures of the above-mentioned conventional technology, for example, PTL 1 is well known.